Prior to the present invention, as shown by Pepe, U.S. Pat. No. 3,584,024, certain isocyanato substituted siloxanes were made by the phosgenation of aminoorgano silane. Although the procedure of Pepe was useful in making particular isocyanate substituted organo polysiloxanes, it was found that the phosgenation of aminoorganosiloxane often resulted in the cleavage of the siloxane linkage and the production of unwanted chlorosilyl substituted orgnosiloxane. Bonnet et al., Bulletin Chemical Society of France 3561 (1972) also showed a similar reaction of aminophenyl substituted polydiorganosiloxanes with phosgene resulting in the production of the corresponding isocyanate.
Even though various prior art procedures have been found for making isocyanatoaryl substituted polydiorganosiloxanes, such procedures often have resulted in the production of undesirable side products, such as chlorosilyl substituted organosiloxanes, which have limited the utility of such isocyanato substituted organosilicon materials.
The present invention is based on my discovery that silicon arylacylazides which can be readily thermally decomposed to the corresponding silicon arylisocyanates, can be made by effecting reaction between an alkali metal azide or organometallic azide and an organo silicon material having at least one chemically combined group of the formula ##STR1## where R is a C.sub.(6-13) divalent aromatic organic radical and X is a halogen radical, such as chloro, bromo or fluoro.
Organo silicon materials having chemically combined groups of formula (1) and a method for making such materials are shown in my copending application Ser. No. 718,039. For Example, an aromatic polyacylhalide, such as terephthaloyl chloride, is reacted with substantially an equivalent amount of a halopolysilane, such as 1,2-dichlorotetramethyldisilane, in the presence of a transition metal catalyst. There is obtained a p-halodiorganosilylbenzoyl halide as the exclusive silylaryl reaction product. Reaction of such p-halodiorganosilylaroylhalide can be used to make the corresponding disiloxane or polydiorganosiloxane having chemically combined units of formula (1).